1. Field of the Invention
This invention relates generally to a circuit for correcting faults in automotive systems having at least two operating states. More particularly, this invention relates to a circuit for correcting faults in a suspension system including adjustable suspension units having multiple operating states.
2. Disclosure Information
Many systems within an automotive vehicle function between two or more operating states. An example of one such system is a suspension system including multistable automotive suspension units. Suspension units defined as "multistable" can be operated in a plurality of predetermined states. Such suspension units provide control of vehicle ride and handling which may be tailored to particular road surfaces and/or driver characteristics. In typical fashion, a particular state chosen for the multistable unit is determined by a control algorithm with inputs from a variety of vehicle parameters. For example, it is known to control a multistable suspension unit by utilizing vehicle linear acceleration, braking, steering activity, and vehicle speed as well as through a manually operable mode switch. U.S. Pat. No. 4,621,833, assigned to the assignee of the present invention, discloses a system for operating multistable suspension units, including feedback of the operating mode of each suspension unit.
Typically in these types of systems, an actuator associated with a switching device places the system into the desired operating state. If the actuator fails to place the system into the desired state, the system may generate an error message and simply shut down until serviced. Systems which compensate for the failure of the actuator to place the system into a desired have been proposed. U.S. Pat. No. 4,700,303 discloses a system for operating a vehicle height adjusting apparatus in the event that an abnormality is detected in the air suspension system of the vehicle. If such abnormality is detected, the control system operates a compressor until a minimum pressure is produced in the suspension units. Similarly, it is known to compensate for loss of ability to control one or more of the suspension units in an automotive vehicle by placing all of the units in a predetermined control position. U.S. Pat. Nos. 4,526,401 and 4,666,180 disclose two control systems in which the inability to operate adjustable suspension units is compensated for by the placement of all the operational suspension units into a "normal" damping force condition. Although such control systems may cope with the loss of control of a suspension unit to a certain extent, the control scheme set forth in the '303, '401 and '180 patents do not disclose means for correcting the faults causing the inability of the suspension units to achieve the desired operating states.
U.S. Pat. No. 4,805,923, assigned to the assignee of the present application, discloses a control system for governing a plurality of multiple operating mode adjustable suspension units. The control system includes a warning means for detecting the inability of an adjustment means to adjust one or more of the suspension units and for generating a warning signal in response to such detection. The control system determines the extent to which the ability to adjust the suspension units has been impaired by commanding the adjustment means to sequentially place the units into at least two of the multiple operating modes and by observing the responses of the suspension unit to these commands. A mode selection means compares the results of the sequential operation of the suspension units by a diagnostic means to a rank order of states of impairment of the suspension unit and selects an obtainable operating mode which is preferred according to such rank order. The control system uses an algorithm which ranks the operating modes of the suspension system to determine which is the best based upon the unit's inability to adjust. However, the '923 patent discloses no means for correcting the inability of the suspension units to be placed into the desired operating states.
U.S. Pat. No. 4,516,076 discloses a fault detection arrangement for a relay switching system in an automatic test system. The test points in a unit under a test are connected to test instruments by the programmed closure of electromechanical relay contacts. A detector circuit is coupled to the interconnected relay contacts which compares a voltage or resistance present on the interconnected relay contacts to a threshold. If a difference between the signal on the interconnecting relay contacts and that threshold persist for a predetermined period, an interrupt signal is generated which prevents further closure of the relay, avoiding failures of the unit under test. There is no teaching or suggestion in the '076 patent of correcting a fault generated by an actuator of the system.
It is, therefore, an object of the present invention to provide a circuit for correcting faults in automotive systems, the circuit having the ability to detect an inability of the system to be placed into one of at least two operating states and to correct that inability.
It is a further object of the present invention to provide such a circuit for correcting faults in an automotive suspension system having multistable adjustable automotive suspension units, the circuit having the ability to detect an inability of the units to be placed into a desired operating state and to correct that inability.
It is an advantage of the present invention that a circuit according to this invention will correct the inability of a suspension unit to be placed into a desired operating state and will minimize the degradation of ride control over the vehicle in the event that one or more of the adjustable suspension units becomes inoperative.
Other objects features and advantages of the present invention will become apparent to those skilled in the art to which this invention pertains.